Water-soluble cutting fluid for slicing silicon ingots

Abstract

A water-soluble cutting fluid for slicing silicon ingots is characterized in that it includes a monoprotic or diprotic aliphatic carboxylic acid (A) having a carbon number (including the carbon in the carbonyl group) of 4˜10, and either a polyprotic organic acid (B) with ΔpKa of 0.9˜2.3 as defined by the following formula (1) or a salt (BA) of said organic acid (B) as essential components: ΔpKa=(pKa 2 )−(pKa 1 )  (1) wherein the dissociation stage, at which the organic acid (B) denoted as n-protic acid H n A, becomes H n-1 A+H + is numbered 1 with an acid dissociation constant expressed as pKa 1 , and the dissociation stage at which the organic acid (B) becomes H n-2 A+H + is numbered as 2 with an acid dissociation constant expressed as pKa 2 .

What is claimed is: 
     
       1. A water-soluble cutting fluid for slicing silicon ingots characterized in comprising an azelaic acid (A), either a polyprotic organic acid (B) with ΔpKa of 0.9˜2.3 as defined by the following formula (1) or an inorganic alkali salts (BA3) of said polyprotic organic acid (B) as essential components, a compound (C), a 50 wt % potassium hydroxide aqueous solution as a pH adjusting agent (D), a naphthalene sulfonic acid formalin condensate as a dispersant (E), and a water:
   ΔpKa=(pKa 2 )−(pKa 1 )  (1)
 
 wherein said polyprotic organic acid (B) comprises citric acid, phthalic acid, or isophthalic acid, said inorganic alkali salts (BA3) comprises citrate salts, phthalate salts, or isophthalate salts having a base derived from lithium, sodium, potassium, calcium, or magnesium, and a dissociation stage, at which said polyprotic organic acid (B) denoted as n-protic acid H n A becomes H n-1 A+H + , is numbered as 1 with an acid dissociation constant expressed as pKa 1 , and the dissociation stage at which said polyprotic organic acid (B) becomes H n-2 A+H +  is numbered as 2 with an acid dissociation constant expressed as pKa 2 ; 
 wherein said compound (C) is propylene glycol, 
 wherein relative to said cutting fluid for slicing silicon ingots, the content of said compound (C) in the said cutting fluid is 60 to 90 wt %. 
 
     
     
       2. The water-soluble cutting fluid of  claim 1 , wherein said polyprotic organic acid (B) is an aromatic polyprotic carboxylic acid (B1) and/or a hydroxyl polyprotic carboxylic acid (B2). 
     
     
       3. The water-soluble cutting fluid of  claim 1 , wherein said compound (C) has a hydrophile-lipophile balance (HLB) value of 8˜45. 
     
     
       4. The water-soluble cutting fluid of  claim 1 , wherein a content of said azelaic acid (A) is 0.001 wt %˜1.0 wt %, relative to said compound (C). 
     
     
       5. The water-soluble cutting fluid of  claim 1 , wherein said polyprotic organic acid (B) is an aromatic polyprotic carboxylic acid (B1) and/or a hydroxyl polyprotic carboxylic acid (B2), and a total content of said aromatic polyprotic carboxylic acid (B1) and said hydroxyl polyprotic carboxylic acid (B2) is 0.01 wt %˜10 wt %, relative to said compound (C). 
     
     
       6. A method for manufacturing slice of silicon ingot, comprising using the water-soluble cutting fluid of  claim 1  and using a fixed abrasive grain wire for slicing the silicon ingot.